GENEVA: Almost everyone in large cities in poor and middle-income countries faces excessively high air pollution, a growing problem that is killing more than three million people each year and “wreaking havoc on human health”, the World Health Organisation said on Thursday.  The UN health agency says more than four out of five city dwellers worldwide live in cities that don’t meet WHO air quality guidelines — 98 per cent in poorer countries and 56 per cent even in high-income countries…